kubuntu-desktop : Depends: software-properties-kde but it is not going to be installed

Try installing software-properties-kde and get

The following packages have unmet dependencies:
  software-properties-kde : Depends: python3-software-properties (= 0.96.24.32.11) but 1.8.8 is to be installed
 E: Unable to correct problems, you have held broken packages.

Try to install python3 from the bionic from bionic-updates

sudo apt install -t bionic-updates python3-software-properties

Install software-properties-kde

sudo apt install software-properties-kde

If it fails try force installing it

sudo dpkg -i --force-overwrite /var/cache/apt/archives/software-properties-kde_0.96.24.32.11_all.deb

Install Kubuntu desktop

sudo apt install kubuntu-desktop

More info here
https://pravin517.wordpress.com/2019/07/14/kubuntu-desktop-depends-software-properties-kde-but-it-is-not-going-to-be-installed/